When is Ghusl required of the One Who has had a Sexual Dream?

Question :

A person believes that what makes Ghusl obligatory for the one who has had a sexual dream is the emission of semen when the sleeper actually dreams about having intercourse, and he will not perform Ghusl unless he experiences this while sleeping. So if he ejaculates semen, while not actually dreaming of sexual intercourse during his sleep, he does not perform Ghusl. He has been doing this for almost eight years, so he is asking about the ruling on these past eight years.

Answer:

It is well known that Ghusl is required when semen is ejaculated due to sexual arousal when awake, and in all cases when asleep, according to the narration of Imam Ahmad, on the authority of 'Ali, may Allah be pleased with him, which states that the Prophet said:
*If you ejaculate water (i.e. semen), then make Ghusl, and if you do not ejaculate, then do not make Ghusl.

and according to the Hadith in the the Two Sahihs, on the authority of Umm Salamah, may Allah be pleased with her, which says that Umm Sulaim, may Allah be pleased with her, said: "O Messenger of Allah! Verily, Allah is not ashamed of the truth, so tell me, is there any obligation upon a woman to perform Ghusl if she has a sexual dream?" The Prophet said:
"Yes, if she observes any fluid.

And the obligation to perform Ghusl is not restricted to sexual intercourse, it is required due to the ejaculation of semen, even if sexual intercourse does not take place, based upon the generality of the Prophet's words:

If you ejaculate water (i.e. semen), then make Ghusl... But if the private parts touch during wakefulness, then Ghusl is always required, whether or not ejaculation takes place, and based upon this (we may say that) this questioner must repeat as much as he can of the prayers which he performed during this period, when he did not make Ghusl after semen was ejaculated because of not actually dreaming about intercourse in his dream. And success comes from Allah.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 2 Pages 68-69